1. Field of the Invention
This invention relates to suspension systems for automobiles and machines which receive mechanical shock, and more particularly, to a method and apparatus for absorbing resonance vibration in a leaf spring of a suspension system.
2. Description of the Related Art
Suspension systems are used to smooth or dampen road vibration which occurs when automotive vehicles are driven. In this regard, suspension systems serve to isolate the sprung portion of the automotive vehicle from the unsprung portion of the automotive vehicle. The term "sprung portion" is used to identify the body and frame of the automotive vehicle which is vibrationally insulated from road vibration, while the term "unsprung portion" is used to identify that portion of an automotive vehicle which is not vibrationally insulated from road vibration. The unsprung portion of the automotive vehicle may typically include the axle, wheels, and drive shaft of the automotive vehicle.
A typical suspension system includes a leaf spring which is attached at each end to the frame of the automotive vehicle. In addition, the center portion of the leaf spring is attached to the drive axle of the automotive vehicle. As the drive axle of the automotive vehicle moves due to road undulations, the leaf spring tends to insulate the axle movement so as to smooth the ride which is felt by the passengers of the automotive vehicle. As those skilled in the art will appreciate, the longer the leaf spring is, the greater the degree to which the leaf spring is able to insulate road vibration and therefore improve ride comfort.
While it is desirable to increase the length of leave springs so as to improve ride comfort, a disadvantage occurs as the length of the leaf spring increases. This is because resonance vibrations can be formed in the open span of the leaf spring (i.e., the unsupported length of the leaf spring) which can become substantial as the length of the open span increases. As a result, wheel hop may occur which degradates not only ride comfort but road holding ability. Accordingly, a need exists for a means to attenuate resonance vibrations in a leaf spring so as to allow longer leaf springs to be used in suspension systems.